1. Field of the Invention
The present invention relates to an adapter for holding a centrifuge tube in a centrifuge rotor cavity, and in particular, to an adapter having two segments, the segments being in some cases joined by a hinge, the hinge axis extending perpendicular to the axis of the adapter.
2. Description of the Prior Art
In the operation of a centrifuge it is important that the size and shape of the tube in which a liquid sample is carried closely conforms to the size and shape of the cavity in the centrifuge rotor in which the tube is received. During centrifugation the centrifugal force exerted on the tube itself and the liquid therein acts to deform the centrifuge tube. A centrifuge tube which does not closely conform to the rotor cavity may thus be deformed to the point of rupture. Even if the tube does not rupture the deformation may make the tube difficult to remove from the rotor cavity. Moreover, even if the deformed tube is removable from the rotor, the return of the tube to its undeformed shape may agitate the contents of the tube to an extent that destroys the sample separation.
When the shape and size of a centrifuge tube does not closely conform to the shape and size of the rotor cavity in which it is to be disposed a device known as a tube adapter is usually employed. The tube adapter has an interior cavity having a shape and size which closely conforms to the shape and size of the centrifuge tube being adapted. The exterior shape and size of the adapter closely conforms to the shape and size of the rotor cavity in which the tube is to be used. The adapter serves to support a tube within the cavity in which it is received and thus serves to prevent deformation of the tube during centrifugation.
Exemplary of an adapter formed of a single unitary member is the device disclosed in U.S. Pat. No. 4,304,356 (Chulay et al.). This adapter supports only the neck region of the centrifuge tube and is fabricated of a material having a lower density than the liquid being carried therein to prevent bottoming of the adapter in the rotor cavity in the event of tube rupture.
Exemplary of an adapter formed of two piece construction is the device shown in U.S. Pat. No. 3,674,197 (Mitchell et al.), assigned to the assignee hereof. This adapter comprises two discrete segments, each of which has an indentation therein. When joined the indentations form a recess for receiving a collapsible bag during centrifugation. The adapter disclosed in this patent includes aperture(s) through which tubes from the bag exit the adapter. Thus, the possibility exists that the bag may extrude through these apertures if the adapter were to undergo centrifugation in a vertical angle rotor.
An adapter arrangement formed of two discrete adapter segments and useful to support the capped end of a centrifuge tube is available as part of the Nalgene Ultra-Lok Tube System sold by Fisher Scientific Incorporated.
U.S. Pat. No. 4,692,137 (Anthony) discloses a tube adapter having two segments which are hinged along the lateral edges of the segments. The hinge axes align in parallel relationship to the axis of the cavity in which the adapter is received. The disposition of hinges along the lateral edges of the segments is believed disadvantageous in that such a disposition may interfere with the insertion or removal of the adapter into or from the rotor cavity.
U.S. Pat. No. 3,998,383 (Romanauskas et al.) and U.S. Pat. No. 4,015,775 (Rohde), both assigned to the assignee of the present invention, disclose centrifuge rotors of the vertical angle type. In such a rotor the axis of the rotor cavities is substantially parallel to the axis of rotation. When using a vertical angle rotor it is necessary that a cap be provided at the mouth of each cavity to impose a vertical restraining force on the tube disposed in the cavity. Even though the tube may be disposed in an adapter received within the cavity, without such a capping arrangement the possibility exists that the pressure of the liquid during centrifugation may rupture the tube. U.S. Pat. No. 3,998,383 (Romanauskas et al.) exemplifies a typical capping arrangement for a vertical angle rotor.
Such capping arrangements must be individually threaded into the rotor body. Moreover, in order to provide proper support it is necessary that the capping arrangement be in intimate contact with the tube. Improper assembly can thus lead to the possibility of tube rupture and/or cap failure. For these reasons such capping arrangements are believed disadvantageous.
In view of the foregoing it is believed advantageous to provide an adapter for use in a vertical angle rotor that eliminates the necessity of a capping mechanism for the rotor cavity.